Effect of Light Wavelengths on the Mycelial Browning of Lentinula edodes Strain Sanjo 701ho

광 파장이 표고 품종 산조 701호 균사의 갈변에 미치는 영향

Abstract

Mycelial browning, which protects the organism from contamination and moisture loss, is essential for sawdust cultivation of Lentinula edodes. The effects of light and light wavelengths on the mycelial browning of the L. edodes Sanjo 701ho strain, and the characteristics of its brown hyphae, were investigated. After the mycelia were cultured on potato dextrose agar medium under fluorescent lamps covered with colored cellophane filters (red, green, and blue) or under light emitted diodes (LED), with wavelengths ranging from 400 to 700 nm (far-red, red, green, and blue), for 14 h per day for 40 days, the mycelial browning rate was measured. The wavelength of fluorescent lamps, which range from 300 to 1,100 nm, was reduced to 360 to 1,022 nm with the use of three colored cellophane filters and the photosynthetic photon flux density was reduced by 42 to 71 % depending on the light wavelength. The browning rate by colony area of mycelia exposed to light was at an average of 64 %, whereas, that of unexposed mycelia was only 5 %. The browning rate was 0.02 % in far-red, 1.5 % in red, 53.8 % in green, 57.3 % in blue, and 64.0 % in fluorescent light. The white mycelia were resilient with actively growing hyphae, filled with cytoplasm, and thin cell walls less than $1{\mu}m$ thick. Conversely, the brown mycelia possessed dead, hard hyphal structures without cytoplasm, but with approximately $2-4{\mu}m-thick$-thick cell walls. In conclusion, lights of varying wavelengths, especially short-wavelength LEDs, are effective for forming dead, brown mycelia of L. edodes, thus, forming a protective functional layer for its living white mycelia.

표고 균사체의 갈변은 균사배양체의 오염과 수분 손실을 방지하는데 매우 효과적이다. 광과 광 파장이 표고 산조701호 품종의 균사체 갈변에 미치는 영향과 갈변 균사의 특징을 이해하고자 하였다. 표고 균사체를 감자한천배지에서 암배양한 후 적색, 녹색, 청색의 색 셀로판 필터를 덥거나, 원적색(far-red), 적색, 녹색, 청색의 light emitted diode (LED)를 매일 14시간씩 40일간 비춘 후 균사배양체의 갈변 면적 비율(갈변율)과 갈변 균사의 특징을 조사하였다. 파장대 범위가 300~1,100 nm인 백색 형광등 빛은 세 가지 각각의 색 셀로판을 통과하면서 360~1,022 nm로 좁아졌고 각 파장별로 photosynthetic photon flux density (PPFD)는 42~71%가 감소하였다. 형광등 빛 처리로 균사체의 갈변율은 면적비율로 평균 64%였으나, 빛을 받지 않은 균사체의 갈변율은 5%에 지나지 않았다. 광 파장별로 표고 균사체의 갈변율은 원적색에서 0.02%. 적색에서 1.5%, 녹색에서 53.8%, 청색에서 57.3% 였다. 그리고 흰색의 미갈변 표고 균사는 세포벽이 $1{\mu}m$ 미만으로 얇고 원형질이 들어찬 생장하는 것이었다. 이에 반하여, 갈변층의 균사는 세포벽이 $2-4{\mu}m$으로 두껍고 세포 내용물이 없는 죽은 것으로 탄력이 없이 단단한 부정형의 구조체였다. 결론적으로 녹색~청색 파장의 빛으로 촉진된 표고 균사의 갈변층은 죽은 조직이지만 그 아래 내부 활력 균사체를 보호하는 중요한 기능층이었다.

Fig. 1. Wavelengths of fluorescent lamp ranging from 300 nm to 1,100 nm. Its maximum photoysnthetic photon flux density (PPFD) was 2.003 μmol/m²/s at 544 nm.

Fig. 2. Wavelengths of fluorescent lamp penetrated through cellophane filter ranging from 300 nm to 1,100 nm. Each light (red, green, blue) had its own wavelength in which the maximum photosynthetic photon flux density (PPFD) value was found.

Fig. 3. Photosynthetically active photon flux density (PPFD) under various wavelengths of light emitted diode (LED) lamp in far-red, red, green and blue. The maximum PPFD was at 732 nm by far-red, 650 nm by red, 520 nm by green, and 458 nm by blue.

Fig. 4. Browning of Lentinula edodes mycelial depending on existence of light. Browning occurred in the non-irradiated medium by 5% only of the colony area (left six plates), and browning occurred in the irradiated medium by 64% of the colony area (right six plates).

Fig. 5. Effects of light wavelengths on browning of Lentinula edodes mycelia cultured in potato dextrose agar (PDA) medium. A, In far-red (702~760 nm); B, Red (646~654 nm); C, Green (502~546 nm); D, Blue (442~480 nm); E, Fluorescent light (300~1,100 nm); F, Brown portion shown as black under fluorescent light.

Fig. 6. White and brown mycelia of Lentinula edodes cultured under different light wavelengths. A, White bumpy colony under red light (646~654 nm); B, Brown colony under blue light (442~480 nm); C, Enlarged white cottony colony surface, ⅹ20; D, Enlarged brown colony surface, ⅹ20; E, Soft thin wall hyaline hyphae on white colony, ⅹ600; F, Hard thick wall brown hyphae on brown colony surface, ⅹ 400.

Table 1. Wavelength and PPFD of LED sources used for browning and primordial formation of Lentinula edodes mycelial culture

Table 2. Browning area rate (%) in Lentinula edodes mycelial culture plates irradiated with various light wavelengths